The present invention relates to a train speed measuring device and method, and more particularly, to a train speed measuring device installed at a train and a train speed measuring method using the same.
In general, one of important functions of a train speed measuring device for a railway vehicle is to apply a brake on and protect a vehicle when the vehicle exceeds the maximum driving speed allowed in a railway in order to evade a collision between the vehicle and a preceding vehicle.
Additionally, in the case of a train automatic operation, a train speed measuring device performs an operation such as brake and acceleration by using a difference between a vehicle's actual speed and a target speed at a vehicle's predetermined driving point. Also, the train speed measuring device calculates an accumulated travelling distance of a train through a measured speed and time value in order to obtain the position of the current train.
In order to perform such a function, an accurate speed calculation of a vehicle is indispensable to the train speed measuring device.
The train speed measuring device installed at a current railway vehicle and for obtaining the safety of a train includes a tachometer installed at a vehicle axle and calculates the train speed by using a speed pulse proportional to the revolution speed of an axle, which is measured from the tachometer according to the movement of the vehicle.
However, such a method may not calculate an accurate speed when abnormal situations such as slip and slide on an axle having a tachometer installed occur due to rainy weather or any other reason.
In more detail, when a slip phenomenon due to the idling of a wheel caused from moisture on a rail occurs, a faster speed than the actual speed of the vehicle is measured. Moreover, when a slide phenomenon due to axle locking caused from a product operation occurs during a train operation, a slower speed than the actual speed of the vehicle is measured. Such a difference between the actual speed and the measured speed of a vehicle may deteriorate the accuracy of exact stop during a vehicle's automatic operation. Additionally, this may be a risk element for overall safe driving.
Furthermore, a slip phenomenon may typically occur in a motor car having a mounted power source.